1. Field of the Invention
The present invention relates in general to a non-volatile memory (NVM) device and operation method thereof. More specifically, the present invention relates to a phase-change non-volatile multi-level cell (MLC) and operation method thereof.
2. Description of Related Art
Conventionally, an electrically programmable non-volatile memory uses its floating gate to store electrons capable of representing information, and one memory cell usually has only one floating gate. The floating gate can stores data of 1 bit since the floating gate is made of conductive material such as polysilicon, etc. Therefore, such memory cell cannot perform a multi-level mode operation.
In addition, a phase-change non-volatile memory is developed in recent years. Data is stored by using different resistant properties at different phases of the conductive phase-change material. For example, U.S. Pat. No. 6,750,469 discloses a phase-change non-volatile storing device and driving circuit thereof, U.S. Pat. No. 6,759,267 discloses a method for making a phase-change non-volatile memory, and U.S. Pat. No. 6,757,190 discloses a single-level metal memory cell with a capping layer made of chalcogenide material.
However, the aforementioned phase-change non-volatile memory cells can only perform an operation of single-level (single bit) mode, and is not able to execute a multi-level mode operation.